Set the sort order's default from the former foldersFirst to mixed, so this is a
change in behavior. I find this useful because it now matches git's order, so if
you look at the diff of a commit, the TOC at the top has the same order as the
file tree you see when entering the commit.
In go 1.22, loop variables are redeclared with each iteration of the
loop, rather than simple updated on each iteration. This means that we
no longer need to manually redeclare variables when they're closed over
by a function.